A 60-year-old man was admitted to our hospital with marked hypercalcemia. He had no symptoms that might be caused by hypercalcemia. Plasma concentrations of calcium and intact parathyroid hormone were 15.2 mg/dl and 103 pg/ml, respectively. Radiological examinations revealed no abnormal findings. His calcium-creatinine clearance ratio was calculated to be 0.004, thus he was diagnosed as having hypocalciuric hypercalcemia. Familial hypocalciuric hypercalcemia was a plausible diagnosis, however, gene analysis of his calcium-sensing receptor (CaSR) revealed no mutation. The patient was thought to be a case of hypocalciuric hypercalcemia without mutation in the CaSR gene.